C6

The C6 paper size has dimensions of 114 x 162 mm, making it the seventh largest size in the C series of envelopes defined in ISO 269 (withdrawn in 2009). With a surface area of 0.017 m2, C6 is a commonly used envelope size. As part of the C series based on geometric means between A and B series sheets, C6 falls between A6 (105 x 148 mm) and B6 (125 x 176 mm). A key use of C6 envelopes is mailing letters, invoices, sheets of paper, and other smaller documents, as C6 provides more space than a standard business envelope. The C6 and other C sizes originate from early 20th century German efforts to define paper sizes based on geometric principles, later included in ISO standards.